I added wire-stubs to furnish twist-together jumpers for the incoming wire (easier to add the stubs on the bench, than to deal with the screw-connectors, crouched in a dark corner).
I wanted to check continuity, so I cut a modular cord in half and bared the wires on one half so I could use an ammeter to check.
What I found was that black & yellow are reversed, and red & green are reversed. The colors are that way on the plate that I bought (short wires with forked terminals in the ends, under the screw-heads). Is this normal? Does it make a difference? It seems to me that if it didn't make any difference, there would be no point to having four wire colors--two of one color, and two of another color would do it.